Question

如何从本机JavaScript有效地将参数列表发送到Emscripten Web Worker？我的数据（参数集）是Float32Array，UInt16Array，int等大型数组的不均匀组合。下面的示例有效，但我不能使用列表，字典或使用int混合使用TypedArrays的元组的任何其他方法。目前，除非输入是单个TypedArray，否则它将转换为几个字节。例如，以下行将发送三个单个字节，每个参数一个。

        test_data_worker([b8verts, 150000, b8faces]);  // doesn't work

我的问题实际上是如何将元组编码为C结构。我可以使用诸如struct.js之类的库，但它们效率低下（需要转换，并且参数不可转移）。 Emscripten对这种情况有什么解决方案。请注意，我的特殊要求是我希望我的JavaScript postMessage()直接进入Emscripten编译的C ++函数，而不是由正面的发送者C ++程序或工作者端的接收器JavaScript代码调解。 / p>

<html>
<script>
    'use strict';
    var worker = new Worker('./emworker.compiled.js');

    var api_info = {
        test: {
            funcName: "worker_function",
            callbackId: 3,
        },
    };

    function test_data_worker(arguments_data_buffer) {
        // The protocol used by Emscripten
        worker.postMessage( {
                funcName: api_info.test.funcName,
                callbackId: api_info.test.callbackId,
                data: arguments_data_buffer,
                // 'finalResponse': false,
        }
        // , [arguments_data_buffer]  //uncommet for transferable
       );
    }

    function demo_request() {
        var verts = new Float32Array([3.141592651234567890123456780,1,2, 3,4,5, 6,7,8, 9,0.5,1.5]);
        var faces = new Uint16Array([0,1,2, 1,2,3, 0,1,3, 0,2,3]);
        var b8verts=new Uint8Array(verts.buffer);
        var b8faces=new Uint8Array(faces.buffer);

        test_data_worker(b8verts);  // b8verts.buffer to make it transferrable
// Desired:
        //test_data_worker([b8verts, b8faces]);  // Doesnt work. sends two bytes instead
        //test_data_worker([b8verts, 60, b8faces]);  // doesnt work
        //test_data_worker({verts:b8verts, d:60, faces:b8faces});  // doesnt work
    }


    worker.addEventListener('message', function(event) {
        // event.data is {callbackId: -1, finalResponse: true, data: 0}
        switch (event.data.callbackId) {
            case api_info.test.callbackId: //api_revlookup.:
                // console.log("Result sent back from web worker", event.data);
                // Reinterpret data
                var uint8Arr = event.data.data;
                var returned_message = String.fromCharCode.apply(null, uint8Arr)
                console.log(returned_message);
                break;
            default:
                console.error("Unrecognised message sent back.");
        }
    }, false);

    demo_request();
    console.log("request() sent.");
</script>
</html>

和Worker的C ++代码就像

#include <iostream>
#include <emscripten/emscripten.h>

extern "C" {
    int worker_function(void* data, int size);
}

std::string hexcode(unsigned char byte) {
    const static char codes[] = "0123456789abcdef_";
    std::string result = codes[(byte/16) % 16] + ( codes[byte % 16] + std::string());
    return std::string(result = codes[(byte/16) % 16] + ( codes[byte % 16] + std::string()));
}


int worker_function(void* data, int size) {
    {
    std::cout << "As bytes: ";
    size_t i = 0 ;
    char* char_data = (char*)data;
    for (; i < size; ++i) {
        std::cout << hexcode((char_data)[i]) << " ";
    }
    std::cout << std::endl;
    }

    {
    std::cout << "As float: ";
    float* typed_data = (float*)data;
    size_t typed_size = (size + sizeof(float)-1) / sizeof(float);
    for (size_t i = 0; i < typed_size; ++i) {
        std::cout << typed_data[i] << " ";
    }
    std::cout << std::endl;
    }

    std::string result = std::string("I received ") + std::to_string(size) + " bytes.";
    char* resstr = (char*)result.c_str();
    emscripten_worker_respond(resstr, result.size()); // not needed really
    return 314;  // ignored
}

void worker_function2(float*verts, int numverts, int*faces, int numfaces) {
    //
}

int main(){return 0;}

使用以下方式使用Emscripten编译：

em++  -s EXPORTED_FUNCTIONS="['_main', '_worker_function' , '_worker_function2' ]" \
  -s NO_EXIT_RUNTIME=1 \
  -s DEMANGLE_SUPPORT=1 \
  -s BUILD_AS_WORKER=1 -DBUILD_AS_WORKER  \
  -pedantic -std=c++14 \
  emworker.cpp \
  -o ./emworker.compiled.js

Web worker上的我的API需要发送和接收多种类型的元组，即它将具有如下输入和输出：

typedef struct vf_pair {
    std::vector<float> verts,  // or a pair<float*,int>
    std::vector<int> faces
} mesh_geometry;
int query_shape(char* reduce_operator, char* shape_spec_json, float* points, int point_count);
struct vf_pair get_latest_shape(int obj_id);
struct vf_pair meshify(char* implicit_object);

Answer 1

您可以找到我在以下回购中使用的模式。这是有效的。它与Web Workers来回交换大型类型的数组和原始类型的值：

https://github.com/sohale/implisolid/blob/master/js_iteration_2/js/implisolid_worker.js

如何直接从本机JavaScript前端与Emscripten Web Worker进行交互

1 个答案: